1. Technical Field
This invention relates generally to trucks and trailers. More particularly, this invention relates to stairs for use on a truck or trailer body. Specifically, this invention is directed to a stair assembly which includes a step assembly that is retractable into a cavity in the body of the vehicle for storage and is extendable therefrom when needed; and the stair assembly includes strategically placed supports for supporting the step assembly when in either of the storage or operational positions.
2. Background Information
Trucks and trailers are typically built so that their working surfaces are positioned some distance vertically from the ground. Consequently, when it is necessary for the truck driver or some other worker to climb onto the working surface, such as the bed of a flatbed trailer, the vertical distance from the ground to the bed makes getting on and off the bed potentially hazardous.
In order to address this situation, a variety of retractable stair systems have been proposed in the prior art. For example, U.S. Pat. No. 2,642,217 to Jennings discloses a retractable ladder for vehicles. A pair of rails is mounted on the underside of a truck body and each rail includes a longitudinal slot. The ladder includes a first end and a second end. Pins are provided at the first end and these pins are engaged in the slots and act as pivots to move the ladder from a horizontal storage orientation to an angled use orientation, and the pins enable the ladder to slide inwardly between the rails when in a horizontal position. A leaf spring keeps the ladder in its storage position and a catch is also provided to lock the ladder in the storage location beneath the truck body. A handle is provided to enable the driver to lift the ladder over the catch and move it into the operational position.
U.S. Pat. No. 3,756,622 to Pyle et al discloses a step assembly comprised of a frame that is secured to the underside of the truck or trailer and a slider that is able to move into and out of the frame. The frame is comprised of at least two U-shaped channels that are configured and oriented to receive the slider therein. The slider is comprised of two L-shaped channels that have a number of step members pivotally engaged therebetween. The slider is manually lifted upwardly so that it is horizontally aligned with the U-shaped channels and is then slid into the frame. When the slider is in this horizontal orientation, each step is aligned with the plane of the slider. When the driver needs to use the stairs, he slides the slider out of the frame so that it is initially horizontally disposed. The front edge of the frame includes a downwardly extending region that permits the driver to then rotate the slider into a position where it engages the ground. Stops on the frame prevent the slider from being accidentally withdrawn therefrom. As the slider rotates into engagement with the ground, the steps pivot relative to the slider from a first position where they are aligned with the plane of the slider, to a second position where they are angled relative to the plane of the slider and are in a horizontal orientation for use by the driver.
U.S. Pat. No. 4,139,078 to Keller is fairly similar to the device disclosed by Jennings in U.S. Pat. No. 2,642,217 except it includes first and second retaining members. The first retaining member is a cord and hook which keep the ladder secured within a storage compartment beneath the truck bed when the ladder is not in use. The device further includes a second retaining member in the form of wedge-shaped abutments which prevent the ladder from being entirely withdrawn from the storage compartment when it is moved from a storage position to an operational position.
U.S. Pat. No. 5,205,603 to Burdette, Jr. discloses a telescoping ladder assembly that slides into and out of a cavity in the tailgate of a truck bed. Parallel grooves are provided in the tailgate and a pair of runner plates is received in these grooves. The runner plates are generally planar members and each defines a slot therein. Axles secured to one end of a first ladder section are engaged in these two opposed slots and this arrangement pivotally engages the first ladder section to the runner plates and also permits the first ladder section to slide along the grooves when in a horizontal orientation. The first ladder section is made up of two U-shaped legs and a plurality of steps that extend between the steps. A second ladder section is engaged with the first ladder section so that it is able to telescope inwardly and outwardly relative to the first ladder section. A locking mechanism secures the first and second sections together. When the device is to be used, it is first moved to a collapsed position by sliding the second ladder section along the legs of the first ladder section so that the second ladder section is disposed adjacent the first ladder section. The collapsed ladder is then pivoted about the axles at the one end of the first ladder section so that it is generally horizontal and aligned with the plane of the two runner plates. The collapsed ladder is pushed toward the end of the tailgate and this movement causes the collapsed ladder to slide into the cavity in the tailgate. The ladder is subsequently removed therefrom by reversing these steps.
U.S. Pat. No. 5,228,707 to Yoder discloses an automatic stepladder assembly that moves between a storage area beneath the vehicle and an operational position in front of the vehicle. The storage area is located beneath the floor of the vehicle and is accessed through an opening in the side wall of the vehicle. The stepladder assembly is comprised of a staircase, a slider and a driver. The staircase includes two parallel, spaced apart casings and a plurality of steps that are fixedly mounted between the casings. The orientation of the steps relative to the casings does not change as the stepladder assembly is moved back and forth between a storage position and an operational position. The staircase is pivotally connected to the slider at its upper end by pins. The slider includes two parallel side walls and two cross walls that are secured to each other in a generally rectangular configuration. A pair of parallel, horizontally-oriented slide rails is connected to the vehicle frame and extends for a distance under the vehicle. The slide rails are generally C-shaped or U-shaped in cross-section and open toward each other. The staircase and slider ride within these rails between a storage position and an operational position. A roller disposed between the rails and at the edge of the vehicle frame and a motor aid in moving the staircase between the storage and operational positions. When the stepladder moves to the operational position, the slider extends for a distance outwardly beyond the side of the vehicle and a top wall of the slider becomes the first step in the stepladder.
While these devices serve the purposes for which they were intended, there is still a need in the art for a stair assembly that is quickly and readily moved from a storage position to an operational position, and which provides a safe and secure way to climb onto and off of a truck bed